McFarland, K. P. | Search bioRxiv

bioRxiv2023

Insect Pollinators: The Time is Now for Identifying Species of Greatest Conservation Need

Severe declines in the abundance of insects, including economically and ecologically important pollinators are alarming conservationists and the public. Yet despite these increasingly well documented declines, relatively few pollinating insects other than some butterflies and bumble bees have appeared as Species of Greatest Conservation Need (SGCN) in State Wildlife Action Plans, decadal-scale blueprints for wildlife conservation efforts across the United States that require updating in 2025. Species absent from SGCN lists are ineligible for congressionally appropriated State Wildlife Grants that direct millions of dollars annually for their conservation. In the past, knowledge about the distribution and abundance of many insect pollinators was too poor to identify those meeting state guidelines for inclusion as SGCN. Using case studies from 4 northeastern states, we demonstrate that sufficient conservation status data now exists for many pollinators, including bees, butterflies, moths, beetles, and flower flies, to identify at-risk species meriting inclusion on SGCN lists in many states. Doing so will increase funding available for surveys, habitat protection and enhancement, and other conservation activities that will benefit this vitally important guild.

ecology↗

bioRxiv2019

Climate change and local host availability drive the northern range boundary in the rapid northward expansion of the eastern giant swallowtail butterfly

AimsSpecies distributions result from both biotic and abiotic interactions across large spatial scales. The interplay of these interactions as climate changes quickly has been understudied, particularly in herbivorous insects. Here, we investigate the relative impacts these influences on the putative northern range expansion of the giant swallowtail butterfly in North America. LocationNorth America. Time period1959-2018. Major taxa studiedEastern Giant swallowtail, Papilio cresphontes (Lepidoptera: Papilionidae); common hop tree, Ptelea trifoliata; common prickly ash, Zanthoxylum americanum; southern prickly ash, Zanthoxylum clava-herculis (Saphidales: Rutaceae). MethodsWe used data from museum collections and citizen science repositories to generate species distribution models. Distribution models were built for each species over two time periods (T1 = 1959-1999; T2 = 2000-2018). ResultsModels for P. cresphontes and associated host plants had high predictive accuracy on spatially-explicit test data (AUC 0.810-0.996). Occurrence data align with model outputs, providing strong evidence for a northward range expansion in the last 19 years (T2) by P. cresphontes. Host plants have shifted in more complex ways, and result in a change in suitable habitat for P. cresphontes in its historic range. P. cresphontes has a northern range which now closely aligns with its most northern host plant - continued expansion northward is unlikely, and historic northern range limits were likely determined by abiotic, not biotic, factors. Main conclusionsBiotic and abiotic factors have driven the rapid northern range expansion in the giant swallowtail butterfly across North America in the last 20 years. A number of bioclimatic variables are correlated with this expansion, notably an increase in mean annual temperature and minimum winter temperature. We predict a slowing of northward range expansion in the next 20-50 years as butterflies are now limited by the range of host plants, rather than abiotic factors.

ecology↗